The ability of ligands for the estrogen receptor to inhibit inflammatory gene expression (causing a reduction of cytokines, chemokines, adhesion molecules and inflammatory enzymes) is believed to provide a means to treat the inflammatory component of diseases such as atherosclerosis, myocardial infarction (MI), congestive heart failure (CHF), inflammatory bowel disease and arthritis. Other potential therapeutic indications for these type of molecules include type II diabetes (Cefalu, J Womens Health & Gender-based Med. 2001, 10, 241 & Yuan et al., Science, 2001, 293, 1673), osteoarthritis (Pelletier et al., Arthr. & Rheum.,2001, 44:1237 and Felson et al. Curr Opinion Rheum, 1998, 10, 269) asthma (Chin-Chi Lin et. al., Immunol. Lett., 2000, 73, 57), Alzheiemer's disease (Roth, A. et. al., J. Neurosci. Res., 1999, 57, 399) and autoimmune diseases such as multiple sclerosis and rheumatoid arthritis.
A common component of these chronic inflammatory conditions is suspected to be polymorphonuclear leukocyte and monocyte infiltration into the site of damage through increased expression of cytokines and adhesion molecules responsible for their recruitment. Overproduction of the cytokine interleukin (IL-6) has been associated with states of chronic inflammation (Bauer M. A., Herrmann F., Ann. Hematol., 1991, 62, 203). Synthesis of the IL-6 gene is induced by the transcription factor nuclear factor κB (NF-κB). Interference at this step in the inflammatory process can effectively regulate the uncontrolled proliferative process that occurs in these chronic conditions.
In endothelial cells, 17β-estradiol (E2) inhibits IL-1β induced NF-κB reporter activity and IL-6 expression in an ER dependent fashion (Kurebayashi S. et. al., J. Steroid Biochem. Molec. Biol., 1997, 60, 11). This has been said to correlate with anti-inflammatory action of E2 in vivo as confirmed in different animal models of inflammation. In models of atherosclerosis, E2 was shown to protect endothelial cell integrity and function and to reduce leukocyte adhesion and intimal accumulation (Adams, M. R. et al., Arterio., 1990, 1051, Sullivan, T. R. et al. J. Clin. Invst. 1995, 96, 2482, Nathan, L. et. al., Circ. Res., 1999, 85, 377). Similar effects of estrogen on the vascular wall have also been demonstrated in animal models of myocardial infarction (Delyani, J. A. et al., J. Molec. Cell. Cardiol., 1996, 28, 1001) and congestive heart failure. Clinically, estrogen replacement therapy (ERT) has been demonstrated to reduce the risk of mortality in patients with both CHF (Reis et. al., J. Am. Coll. Cardio., 2000, 36, 529) and MI (Grodstein, F. et. al., Ann. Int. Med., 2000, 133, 933, Alexander et. al., J. Am. Coll. Cardio., 2001, 38, 1 and Grodstein F. et. al., Ann. Int. Med, 2001, 135,1). In ERT, clinical studies demonstrated an influence of E2 on the decrease in the production of β-amyloid 1-42 (Aβ42), a peptide central for the formation of senile plaques in Alzheimer's disease (Schonknecht, P. et. al., Neurosci. Lett., 2001, 307, 122).
17-β-estradiol, however, also strongly stimulates creatine kinase expression. Thus, in ERT some potential unwanted side effects, such as an increase risk of cardiovascular events in the first year of use, have been demonstrated (Hulley, S. et. al., J. Am. Med. Assoc., 1998, 280, 605) as well as proliferative effects on uterine and breast tissue.